Chronic hypertension is one of the most common serious complications encountered during pregnancy. This is not surprising because, according to the National Health and Nutrition Examination Survey (NHANES) from the Centers for Disease Control and Prevention (2011), the average prevalence of hypertension in women aged 18 to 39 years is approximately 7 percent. The incidence of chronic hypertension in pregnancy is variable depending on population vicissitudes. In a study of more than 56 million deliveries from the Nationwide Patient Sample, 1.8 percent of births in 2007 and 2008 were in women with chronic hypertension (Bateman, 2012). The incidence was 1.0 percent in more than 530,000 singleton pregnancies in California in 2006 (Yanit, 2012). And according to the American College of Obstetricians and Gynecologists (2012), the incidence may be up 5 percent. Despite this substantive prevalence, optimal management has not been well studied. It is known that chronic hypertension usually improves during early pregnancy. This is followed by variable behavior later in pregnancy and importantly, by its unpredictable development of superimposed preeclampsia, which carries increased risks for maternal and perinatal morbidity and mortality.
To define chronic hypertension, first, the range of normal blood pressure levels must be established. This is not a simple task because, like all polygenic-determined biological variants, blood pressure norms differ between populations. And, within these norms, there are wide variations between individuals. Moreover, these are also greatly influenced by numerous epigenetic factors. For example, blood pressure not only varies between races and gender, but the pressures—especially systolic—increase directly with increasing age and weight. Pragmatically then, normal adults have a wide range of blood pressures, but so do those with chronic hypertension.
After these variables are acknowledged, an important consideration for any population is the attendant risks of chronic hypertension. There is an increasing incremental rate of cardiovascular, cerebrovascular, and renal disease that follows increasing levels of both diastolic and systolic pressures (Kotchen, 2012).
Definition and Classification
For the foregoing reasons, it seems logical that chronic hypertension would be defined as some level of sustained blood pressure that is associated with an increase in acute or long-term adverse effects. For many years in the United States, these values were based primarily on actuarial tables constructed using data derived from white adult males and compiled by life insurance companies. These “norms” disregarded interrelated factors such as ethnicity and gender as well as other important covariants. The importance of race, for example, was emphasized by Kotchen (2012), who cites statistics derived from 65 million American adults. In this study, the incidence of hypertension—defined as blood pressure > 140/90 mm Hg—was 34 percent in blacks, 29 percent in whites, and 21 percent in Mexican Americans.
For many years, guidelines for diagnosis, classification, and management of chronic hypertension have been promulgated ...